xen: make -fstack-protector work under Xen - linux-dev - Linux kernel development work

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author	Jeremy Fitzhardinge <jeremy.fitzhardinge@citrix.com>	2009-08-27 12:46:35 -0700
committer	Jeremy Fitzhardinge <jeremy.fitzhardinge@citrix.com>	2009-09-09 16:37:39 -0700
commit	577eebeae34d340685d8985dfdb7dfe337c511e8 (patch)
tree	047aa135d143ed12035ca04433e563b948f9b059 /include/linux/ssb
parent	Linux 2.6.31-rc9 (diff)

xen: make -fstack-protector work under Xen

-fstack-protector uses a special per-cpu "stack canary" value. gcc generates special code in each function to test the canary to make sure that the function's stack hasn't been overrun. On x86-64, this is simply an offset of %gs, which is the usual per-cpu base segment register, so setting it up simply requires loading %gs's base as normal. On i386, the stack protector segment is %gs (rather than the usual kernel percpu %fs segment register). This requires setting up the full kernel GDT and then loading %gs accordingly. We also need to make sure %gs is initialized when bringing up secondary cpus too. To keep things consistent, we do the full GDT/segment register setup on both architectures. Because we need to avoid -fstack-protected code before setting up the GDT and because there's no way to disable it on a per-function basis, several files need to have stack-protector inhibited. [ Impact: allow Xen booting with stack-protector enabled ] Signed-off-by: Jeremy Fitzhardinge <jeremy.fitzhardinge@citrix.com>

Diffstat (limited to 'include/linux/ssb')

0 files changed, 0 insertions, 0 deletions

#include <linux/compiler.h> #include <linux/export.h> #include <linux/cryptohash.h> #include <linux/bitops.h> /* F, G and H are basic MD4 functions: selection, majority, parity */ #define F(x, y, z) ((z) ^ ((x) & ((y) ^ (z)))) #define G(x, y, z) (((x) & (y)) + (((x) ^ (y)) & (z))) #define H(x, y, z) ((x) ^ (y) ^ (z)) /* * The generic round function. The application is so specific that * we don't bother protecting all the arguments with parens, as is generally * good macro practice, in favor of extra legibility. * Rotation is separate from addition to prevent recomputation */ #define ROUND(f, a, b, c, d, x, s) \ (a += f(b, c, d) + x, a = rol32(a, s)) #define K1 0 #define K2 013240474631UL #define K3 015666365641UL /* * Basic cut-down MD4 transform. Returns only 32 bits of result. */ __u32 half_md4_transform(__u32 buf[4], __u32 const in[8]) { __u32 a = buf[0], b = buf[1], c = buf[2], d = buf[3]; /* Round 1 */ ROUND(F, a, b, c, d, in[0] + K1, 3); ROUND(F, d, a, b, c, in[1] + K1, 7); ROUND(F, c, d, a, b, in[2] + K1, 11); ROUND(F, b, c, d, a, in[3] + K1, 19); ROUND(F, a, b, c, d, in[4] + K1, 3); ROUND(F, d, a, b, c, in[5] + K1, 7); ROUND(F, c, d, a, b, in[6] + K1, 11); ROUND(F, b, c, d, a, in[7] + K1, 19); /* Round 2 */ ROUND(G, a, b, c, d, in[1] + K2, 3); ROUND(G, d, a, b, c, in[3] + K2, 5); ROUND(G, c, d, a, b, in[5] + K2, 9); ROUND(G, b, c, d, a, in[7] + K2, 13); ROUND(G, a, b, c, d, in[0] + K2, 3); ROUND(G, d, a, b, c, in[2] + K2, 5); ROUND(G, c, d, a, b, in[4] + K2, 9); ROUND(G, b, c, d, a, in[6] + K2, 13); /* Round 3 */ ROUND(H, a, b, c, d, in[3] + K3, 3); ROUND(H, d, a, b, c, in[7] + K3, 9); ROUND(H, c, d, a, b, in[2] + K3, 11); ROUND(H, b, c, d, a, in[6] + K3, 15); ROUND(H, a, b, c, d, in[1] + K3, 3); ROUND(H, d, a, b, c, in[5] + K3, 9); ROUND(H, c, d, a, b, in[0] + K3, 11); ROUND(H, b, c, d, a, in[4] + K3, 15); buf[0] += a; buf[1] += b; buf[2] += c; buf[3] += d; return buf[1]; /* "most hashed" word */ } EXPORT_SYMBOL(half_md4_transform);


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